Recently, with the increase of energy consumption, development of solar cells converting solar energy into electric energy is in progress.
Particularly, a CIGS-based solar cell, which is a pn hetero junction device having a substrate structure including a glass substrate, a metal rear electrode layer, a p-type CIGS-based light absorbing layer, a high-resistance buffer layer, and an n-type window layer has been widely used.
In this solar cell, studies to improve the electrical and optical properties of the solar cell such as low resistance, high transmittance and the like are proceeding.